Hybrid electric vehicles (HEVs) utilize both an internal combustion engine and one or more electric machines (e.g. motors/generators) to generate power and torque. The electric motor/generator within a HEV provides the vehicle with additional degrees of freedom in delivering the driver-demanded torque and is also typically used to start the vehicle's engine.
Conventionally, the internal combustion engine is connected to the one or more electric machines through the use of a shaft. The shaft has a damper coupled thereto whose purpose is to isolate the transmission from fluctuations in the internal combustion engine torque output. However, the damper has a characteristic resonance frequency that causes amplification of vibrations and oscillations experienced by the shaft. These vibrations and oscillations become audible to a vehicle operator and are undesirable.
Nevertheless, in order to start the vehicle's engine, the starter/generator receives power from an onboard electrical power supply such as a battery. During cold temperature starting conditions, these batteries provide limited performance. The temperature of the battery can drastically affect its power output and energy storage capacity.
Efforts have been made to overcome the cold starting limitations associated with conventional HEV starting systems. These efforts include utilizing different battery technologies in parallel, self-heating the battery core by use of resistive elements, and providing an auxiliary climate control system for the battery. However, these systems require additional hardware and packaging considerations that increase cost and system complexity.
The present invention was conceived in view of these and other disadvantages of conventional systems.